In recent years, it has been examined to use an electric winch driven by an electric motor as a winch mounted on a crane or the like to perform lifting work. The use of the electric winch has an advantage of ability to perform a regenerative action, that is, an operation for converting kinetic energy generated by a drop of a target object during lowering of the target object (rotation energy of the electric motor) into electric energy and collecting the electric energy.
For example, Japanese Unexamined Patent Publication No. 2012-121675 discloses using an electric generator having a power generation function as an electric motor for driving an electric winch mounted on a mobile crane and performing a control for causing the electric generator to perform a braking action for the electric winch and to output regenerative power.
It is required of such a construction machine including an electric winch to generate regenerative power as much as possible for improvement of operation efficiency while applying a proper braking force (a braking force sufficient for realizing a predetermined braking action) to the electric winch for high safety. Japanese Unexamined Patent Publication No. 2012-121675, although disclosing braking and regeneration by use of an electric generator, indicates no suggestion about control for simultaneously satisfying the above two different demands.